common: Tick an unselected row when enter is pressed

This makes the dialog easier to use via keyboard navigation since
otherwise we would just dismiss the dialog with the current selection
on enter when the user actually intended to change the selection.

https://bugzilla.gnome.org/show_bug.cgi?id=752001

panels/common/cc-language-chooser.c

@@ -368,6 +368,26 @@ row_activated (GtkListBox        *box,
         }
 }
 
+static void
+activate_default (GtkWindow *window,
+                  GtkDialog *chooser)
+{
+        CcLanguageChooserPrivate *priv = GET_PRIVATE (chooser);
+        GtkWidget *focus;
+        gchar *locale_id;
+
+        focus = gtk_window_get_focus (window);
+        if (!focus)
+                return;
+
+        locale_id = g_object_get_data (G_OBJECT (focus), "locale-id");
+        if (g_strcmp0 (locale_id, priv->language) == 0)
+                return;
+
+        g_signal_stop_emission_by_name (window, "activate-default");
+        gtk_widget_activate (focus);
+}
+
 static void
 cc_language_chooser_private_free (gpointer data)
 {
@@ -433,6 +453,9 @@ cc_language_chooser_new (GtkWidget *parent)
 
         gtk_window_set_transient_for (GTK_WINDOW (chooser), GTK_WINDOW (parent));
 
+        g_signal_connect (chooser, "activate-default",
+                          G_CALLBACK (activate_default), chooser);
+
         return chooser;
 }